1. Field of the Invention
The present invention relates to a method for limited copying or recording of an information signal such as audio signal, video signal, etc., a system for controlled copying or recording of information signal, using the method, and an information signal recording apparatus also using the method.
2. Description of the Related Art
Recently, as the digital content service by the Internet, compact disc (CD), digital video disc (DVD), etc. has become popular, illegal copying of a digital content has become a serious matter of piracy. To cope with this problem, it has been proposed to add, to a digital content, copy-controlling information used to prevent the digital content from illegally being copied.
The systems having so far been proposed to prevent such illegal copying mainly include a system for disabling copying of any digital content supplied from a specified information source, a system for enabling to copy a digital content once while disabling further copying of the digital content once copied (generation-managing copy control system). The former system is applied for an original software produced and sold by a content maker, such as a digital data recorded in a DVD-ROM. The latter system (generation-managing copy control system) is applied for information to be broadcast in a broadcasting medium, for example.
The generation-managing copy control systems should desirably be able to effectively manage the copy generation. The copy control systems adapted to manage the copy generation include SCMS (Serial Copy Management System) for audio signals, and CGMS (Copy Generation Management System) for video signals.
The SCMS system is such that a copy disable/enable flag transmitted together with a digital audio signal, and a category code indicative of a digital audio source such as a compact disc (CD), digital audio tape (DAT) or the like, are used to provide a serial-copy control for enabling to copy a digital audio signal only once.
More specifically, the SCMS system controls the copy generation of a digital audio signal using SCMS information including a copy disable/enable flag and category code which are transmitted along with the digital audio signal to enable copying of the digital audio signal only at one generation while disabling further copying of the digital audio signal copied at the previous generation.
The CGMS system is such that for transmission of an analog video signal for example, additional information of 2 bits for control of copying are superposed on the analog video signal in a predetermined horizontal zone of the vertical blanking interval thereof, while for transmission of a digital video, additional information of 2 bits for control of copying is added to the digital video data.
The 2-bit information used in the CGMS system (will be referred to as “CGMS information” hereinafter) takes any of the following states:
[00] . . . Copying is enabled.
[10] . . . Copying is enabled for one generation alone.
[11] . . . Copying is disabled.
When the CGMS information added to a video signal takes the status [10], a recording apparatus adopting the CGMS system will decide that the video signal can be copied, and record the video signal which will however have added thereto the CGMS information changed to the status [11] when recorded. When the CGMS information added to a video signal the recording apparatus is going to record is in the state [11], the recording apparatus will be disabled from copying the video signal.
As in the above, the generation-managing copy control systems such as the SCMS and CGMS are adopted to manage the copy generation and enable to copy an information signal such as an audio signal, video signal, etc. only for a private use. Namely, further copying of an information signal once copied can be disabled and thus such a once-copied information signal will not further be copied repeatedly. Therefore, the due profits for the copyrighter of the information signal will not be caused to lessen by any illegal or fraudulent copying of the information signal, and also his or her copyright for the information signal will not be infringed by any such fraudulent copying.
When the SCMS or CGMS system is used to manage the copy generation for copy of an information signal, it is possible to disable further copying into another recording medium of the information signal once copied. Namely, it is disabled to make a second-generation copy from a first-generation copy. However, there is a problem that many copies can be made of the first-generation copy. That is, an original information signal served as recorded in a CD or DVD, for example, from a content maker can be copied limitlessly from the recording media
Also, with use of the so-called high-speed copying technique, an audio or video signal can be copied at a high speed, namely, for a shorter time than the standard reproduction or playing time for the signal. In this case, however since a desired information signal can be copied for a short time, many copies of the information signal can be made for the first generation even if the SCMS or CGMS system is adopted to manage the copy generation and thus many recording media each having an information signal copied thereto can be produced for a relatively short time. If many copies are made of an information signal using the high-speed copying technique, that is, if recording media each having the information signal copied thereto are illegally produced sold by any other person than the author of the information signal or person entitled to have the copyright of the information signal, the author or the entitled person will lose his or her due profits from the information signal to a large extent.
To avoid the above, a copy limiting system has been proposed which allows each of recording apparatuses to hold identification (ID) information on a copied information signal and disables each recording apparatus from copying any information signal having the same ID information as the ID information already held therein. That is, the copy limiting system enables each recording apparatus to copy each information signal only once.
The copy limiting system disables the recording apparatus from further copying any information signal once copied. Therefore, since the above-mentioned high-speed copying technique cannot be used to make many copies of the same information signal when the copy limiting system is adopted, it is possible to positively prevent any fraudulent copying of an information signal and thus protect the copyrighter's due profits which would be lost or reduced due to such fraudulent copying of the information signal.
In this case, however, since the once-copied information signal cannot further be copied using the same recording apparatus by which the information signal has been copied once, copying of the information signal within a range of private use will be limited, which will cause the user not to conveniently use the information signal as the case may be.
Also, the copy limiting system enabling to copy the same information signal only once in each of recording apparatuses, makes it necessary to provide in each recording apparatus a memory capable of storing ID information on all copied information signals, and manage all the ID information stored in the memory. Thus, the load to the recording apparatus will be larger.